The mechanisms of volatile general anesthetics remain unclear. One of the putative targets for volatile general anesthetics is the brain serotonin receptor. This study will test the hypothesis that the 5HT2A receptor will not show a conformational change from anesthesia. The binding of the radiotracer 18F-altanserin will be measured by PET in the presence of an anesthetizing concentration of isoflurane to that in isoflurane's absence will be compared.